The present invention relates to implantable tissue expanders and prostheses. Although the tissue expanders may be used in other areas of the body, one specific application of the inventive subject matter are implantable mammary soft tissue expanders.
Tissue expanders are devices that are implanted beneath the skin and then gradually inflated to stretch the overlying tissue. Expanders are commonly used either to create a pocket for receiving a permanent prosthesis or to generate an increased skin surface area in anticipation of the new skin being utilized for grafting or reconstruction.
Conventional implantable tissue expanders are formed of a silicone polymer shell. After implantation, a fluid such as saline is periodically injected into the expander for expansion. Between injections, the surrounding skin is permitted to stretch and grow to create the increased skin surface.
The saline or other fluid may also be withdrawn from the expander to reduce its volume. In addition, the shell can be partially filled with fluid or gel prior to implantation.
Typically, a tissue expander will be provided with an injection dome, for example, a dome comprising a septum that can be pierced with a hypodermic needle for the introduction of fluid directly into the expander or withdrawal of fluid directly from the expander. However, it can be difficult to accurately locate the injection dome through the overlying tissue. If the injection dome is missed and the needle punctures the shell of the tissue expander adjacent to the injection dome, the expander can leak. Most often, any leaking requires that the expander be removed and replaced.
This problem can be addressed by providing an injection dome that is remote from the tissue expander but is in fluid communication with the expander. Other solutions include eliminating the need for an injection site altogether by forming the expander with a self-sealing shell that can be pierced with a hypodermic needle at any location for the purpose of adding fluid to the shell.
Still further solutions include providing an injection dome surrounded by a self-sealing member that reduces the risk of causing a leak in the tissue expander in the event that the hypodermic needle used to fill the expander accidently misses the injection dome. Such an arrangement reduces the frequency with which expanders require removal due to leakage caused by inadvertent punctures. It is this type of arrangement that is the focus of the present invention, which draws on the teachings of U.S. Pat. No. 6,743,254, the disclosure of which is hereby incorporated by reference herein.